Deep vein thrombosis is a condition resulting from the lack of blood flow in the veins and the condition is related primarily, but not exclusively, to the legs. Blood flow tends to slow down or stop when there is prolonged inactivity, especially when seated, as would happen in an office or when working on computer or at a telephone especially in a cramped space. More specifically deep vein thrombosis occurs when a clot forms in the deep veins within the calf or thigh muscles. It is usually a spontaneous condition that occurs in people especially at risk, such as those with heart disease, those who smoke or consume alcohol and those that are generally overweight.
Any period of prolonged inactivity can generally trigger the condition and medical research suggests that those over forty years of age are at ever increasing risk. Warning signs are pain and tenderness in the leg muscles, redness and swelling of the skin. If the blood clot moves to the lung (a pulmonary embolus), then breathing difficulties can occur. A clot travelling on to the heart can cause death or if it travels to the brain a stroke is a possibility. There are well-documented cases of people suffering from this condition during long haul plane journeys and there have been some deaths attributed to DVT. There is also a risk in work environments where employers need to ensure the standards of health and safety for their workers.
It is to be expected that in office conditions people will stay still in their chairs for extended periods of this time. This cannot be prevented on an individual basis and this is where a problem may arise. Furthermore, at such times, people may for one reason or another remain essentially motionless. This inactivity reduces the blood flow in the legs and the potential problem of DVT becomes a factor.
Regular use of the legs dramatically reduces the risk of DVT. However, the employer has no way of ensuring that suitable exercise is done by their employees, despite the fact that the health and safety of those workers is at least partially the employer's responsibility.
Previous attempts have been made to monitor the movement of patients such as those described in U.S. Pat. Nos. 5,941,836, 6,646,556, 4,536,755, 5,523,742, 4,064,368 and 6,445,298. None of these are designed for or suitable for use by workers in an office environment because they are large, cumbersome, suitable only for lying down and/or unable to distinguish relevant exercise movement from background movement caused by incorrect activity or the motion for example of a wheeled chair upon which the person is sitting.